(1) Field of the Invention
This invention relates to a method and apparatus for detecting where useful image data about a document exists within a stream of successive scans of image data coming from an imaging camera positioned at a scanning line.
(2) Background Information
There is a trend in the processing of documents to move the documents past a scanning line where an imaging camera is located to obtain image data about the document. The camera produces successive scans of image data or pixels as each document is moved past the scanning line. The image data is processed to obtain information or data about the documents.
One of the problems with working with image data is that it is sometimes difficult to extract the useful image data from that image data which does not contain pertinent data about the document. One of the ways of selecting useful image data from a stream of successive scan lines of pixels is to use an external leading edge detector, for example, which is positioned upstream from the scanning line and imaging camera. By knowing the velocity at which a document is being moved towards the scanning line and by knowing how far the leading edge detector is located from the scanning line, a reasonable approximation of the start of the useful image data of the document may be obtained.
Another trend in the processing of documents is to make the machines or terminals which process the documents smaller or to provide the machines with a smaller "footprint". Having external sensors to detect the leading and trailing edges of documents and having external sensors to detect the height of documents passing the imaging camera tend to make the task of making the machines smaller more difficult. Having to process image data which is unnecessary or not pertinent also tends to increase the machine time for processing the image data.